Interactive devices with touch-sensitive screens have become prevalent. Such devices commonly range from large computer displays to smaller hand-held tablet devices, all the way down to small cell phones and data storage devices.
In the past, users of interactive devices with touch-sensitive screens have typically manipulated touch screen-based interfaces through finger/thumb contact/proximity. Increasingly, however, pen-like devices—styli—are being used as an alternative/complement to finger-based input, most frequently in the context of writing, drawing, and painting activities.
Today's styli for interactive touch-screen devices are predominantly passive (not electrically powered) devices, however active styli incorporating electrically powered features (such as switches, pressure sensors, processors, and transmitters) are beginning to appear on the market. Active, electrically powered styli can advantageously provide users with new/additional/different capabilities, which are preferable for supporting particular kinds of tasks and interactions. For example, a stylus with sensor-enabled pressure-sensitivity can support varying the darkness of a virtual drawn line within a sketching application that is operating on a touch-sensitive device that is in communication with the stylus.
In order for an active stylus' powered electronic aspects to function, a source of electrical power is required. Some active styli are powered wirelessly from a device incorporating a screen through inductive coupling. Other active styli are powered through a power cord while in use. However, each of the aforementioned power sources have distinct advantageous and drawbacks. For instance, attached power cords may become tangled or limit mobility.
Still other active styli include their own internal reservoirs for electrical power, such as a replaceable and or rechargeable cell/battery. Styli with their own internal power reservoirs are advantageous in many respects, but require a user to ensure that enough charge is available for use. As a result, users of active styli, which contain their own charge reservoirs, may find that their styli are without power at inopportune times—with no convenient way to address this lack of power.